Digital terrestrial photogrammetric methods for tree stem analysis

A digital camera was used to measure diameters at various heights along the stem on 20 red oak trees. Diameter at breast height ranged from 16 to over 60 cm and height to a 10-cm top ranged from 12 to 20 m. The chi-square maximum anticipated error of geometric mean diameter estimates at the 95 percent confidence level were within ± 4 cm for all heights when obtained at a distance of 12 m or greater. Error increased with increased stem height from ± 3 to ± 7 cm for heights from 1 to 20 m. In general, the error is equivalent to 3 times the instrument precision, which varies with distance. Two-thirds of the volume estimates were within 8 percent of ‘actual’ volumes. _______________________ Diversifying values and increased accountability are forcing today’s natural resource managers to make complex and defensible decisions. Information requirements to make these decisions are expanding in magnitude and variety, especially in forestry. Multiple resource inventories are being developed to maximize the efficiency of data collection for multiple objectives (Lund 1998). Analysis involving the health, volume, growth, change, and potential of forest resources at some level require information about individual stems. Collecting the large amounts of data required for these purposes is slow and expensive. In this paper, a method is set forth using a non-metric digital camera to capture raw data from an individual stem that can later be used for customized analysis. Diameter and height measurements were derived in this study to examine the effectiveness of this method for determining stem volume.